30 BOTANICAL GAZETTE [JULY 
in the zone under consideration, the differences in habit of form 
shade into each other, and in consequence are less distinct than 
those in the adjoining border zones. The prevailing grasslike 
growth-form, the general reduction in size of leaves assumed by 
the different species, is in harmony with the environment. It 
expresses itself not only in external features but also in the ana- 
tomical structure. As an ecological unit, the community of 
plants, identical in type, but different in floristic composition, 
exhibits well within itself the impress of its conditions of life. 
Frc. 5.—A pond in the cranberry-sphagnum association; Decodon is the most 
important mat former making the advance upon the water. 
Differences in aerial functions would be therefore largely species 
characteristics as well as environmental. 
That the plants are adapted to a given average supply of avail- 
able water, but with great specific differences among themselves, 
is further seen in the frail growth of Cephalanthus and Decodon, 
in the small trees of Acer rubrum and Rhus Vernix, and in the 
stunted forms of various other invaders from the neighboring plant 
societies which occur scattered throughout this zone. For the 
past few years thousands of maple, sumach, and alder seedlings 
have been observed to sprout, and yet failed to succeed beyond 
the first year’s growth. Of those which succeeded, the stunted 
growth, the numerous dead branches, the ragged crown of foliage, 
